Here is an example of a QR code having been placed onto a film poster. As you can see it does not detract from the visuals of the poster, but is still large enough to be recognised as a QR code that can be scanned. I would try to employ this universally, making sure the QR code is in the bottom right of the poster, so parents and audience members know where to look when they want to scan the QR code.
What is the function of placing a barcode on a poster?
barcode not is running , how to scan barcode in picture?